* BOJ will debate if Sept, Oct easing was enough - Nishimura * BOJ will take decisive action if risks heighten - Nishimura * Adds BOJ focusing more on downside economic risks * To keep asset-buying scheme until 1 pct inflation in sight * Remarks heighten chance BOJ will ease again in December By Leika Kihara NIIGATA, Japan, Dec 5 The Bank of Japan will debate whether further monetary stimulus is needed to support an economy seen as undershooting forecasts, its deputy governor said, offering the strongest signal to date that it may loosen policy again this month in the face of growing political pressure. Deputy Governor Kiyohiko Nishimura also suggested that while the BOJ's current asset-buying programme remains its key policy easing tool, the central bank will not rule out new ideas to beat deflation, which has plagued Japan for more than a decade. "The BOJ has been and will always be open to any new possibilities in terms of monetary policy steps," he told a news conference in Niigata, northwestern Japan, on Wednesday. The remarks by Nishimura, one of the BOJ's two deputy governors, echo the pessimistic views offered by board member Sayuri Shirai last week, a sign the central bank is leaning toward easing again this month despite boosting asset purchases for two straight months in October. "We took action in September and October because what we thought were risks back in the summer materialised. We must debate and consider whether that was enough, taking into account various data which came out since then," he said. The BOJ has been under intense political pressure to take bolder action to beat deflation. Shinzo Abe, head of a main opposition party which looks set to win a Dec. 16 general election, has called for "unlimited" easing to achieve 2 percent inflation as well as a possible revision to a law guaranteeing the BOJ's independence. Many market players have thus expected the BOJ to ease again at its next policy meeting on Dec. 19-20, to be held just days after the election, or in January. Nishimura's remarks suggest the BOJ likely will not wait until January if upcoming data, such as its closely-watched "tankan" business sentiment survey due on Dec. 14, turn out to be weak. "Hard data for October were tilted less to the downside, but that does not mean downside risks have disappeared, so there is a good rationale for the BOJ to ease this month," said Masamichi Adachi, senior economist at JPMorgan Securities in Tokyo. "I don't think the BOJ will take the more radical measures that some people are arguing for. They're likely to go for a steady increase in asset purchases, maybe even beyond 2013." The 10-year Japanese government bond futures contract hit a near-decade high on expectations of further BOJ easing. STRONGER COMMITMENT The BOJ set a 1 percent inflation target in February and eased four times this year in an effort to revive the economy and show its determination to beat deflation. But the economy shrank 0.9 percent in the September quarter and is expected to contract again this quarter, meeting the popular definition of a recession, as the country deals with the global headwinds such as falling exports to China. Nishimura, a former economics professor, said that while a surprise rebound in factory output in October was a positive sign, the economy may undershoot the central bank's long-term forecasts made in October as weak global growth may delay a recovery in exports and hurt domestic demand. "The BOJ has been and will always be ready to take appropriate and decisive action when the economy deviates from our baseline scenario, or when risks to our scenario materialise," he said in a meeting with business leaders prior to the news conference. Japanese manufacturing activity contracted in November at the fastest pace in 19 months, a survey showed last week. With interest rates virtually at zero, the central bank put in place in 2010 an asset-buying and loan programme as its key monetary easing tool. It has repeatedly topped up the programme, now pledging to pump 91 trillion yen ($1 trillion) via asset buying and market operations. The BOJ will keep its asset-buying programme in place even after the end-2013 deadline for purchases if 1 percent inflation is not foreseen by then, Nishimura said, strenghtening the bank's commitment to ultra-easy policy. He did not specify what new measures could be available besides those already announced by the BOJ, only saying that the central bank will always weigh the costs and benefits in deciding on new policy steps. A former academic and among the BOJ's two deputy governors, Nishimura surprised markets by proposing an expansion in asset purchases last year. His proposal was not accepted by the board at that time. He has voted with the majority since then.